1. Field of the Invention
The present invention is directed to an electro-photographic image forming apparatus such as a printer, a facsimile device, a copy machine, etc., and is particularly directed to a replaceable process cartridge used in such an image forming apparatus.
2. Discussion of the Background
In an image forming device it is known to utilize an image carrier unit having a housing that contains an image carrier. Such an image carrier unit is replaceable to improve efficiency when such an image carrier unit becomes worn out or defective and needs to be replaced. Such an image carrier unit can be formed as a process cartridge that contains a developing device that develops an electrostatic latent image written on the surface of an image carrier and a cleaning unit that cleans a surface of the image carrier. Such a process cartridge also includes a housing with an opening that allows the image carrier to make contact with a transfer member, a paper sheet, etc.
In such an image forming device attention must be paid to avoiding contact with the image carrier through the opening in the housing. Particularly, attention must be paid that a worker's hand does not touch the image carrier when replacing the image carrier unit, or that foreign substances do not adhere to the image carrier. Light should also be prevented from impinging on the image carrier through the opening to prevent breakdown of the image carrier surface. Paying attention to the above-noted matters is particularly significant because the image carrier unit can be replaceably installed by a worker, and at that point must be handled by the worker.
Before an image carrier unit is installed into an image forming apparatus, the opening portion in the housing can be covered with a seal member. After the image carrier unit is installed into the image forming apparatus, the seal member is removed from the image carrier unit. An example of such an operation is disclosed in Japanese Patent Laid Open No. 59-61848. In that device a seal member is formed of a material such as a polyester film, which has a drawback that such a material is difficult to tear.
The present inventors recognized that an image carrier is particularly susceptible to damage because when a toner image on an image carrier is transferred to a transfer member or a paper sheet, it is necessary that some outer part of the image carrier protrude from an opening of the housing to contact the transfer member or paper sheet. As a result it becomes more difficult to protect that protruding portion of the image carrier.
The present inventors also recognized that when the opening of the housing is covered by a hard seal member, the outer layer of the image carrier may become damaged from contact with or rubbing against the hard seal member. Particularly when transporting the image carrier unit, for example prior to installing the image carrier unit, vibration caused by rotation of the image carrier may more easily result in contact between the outer layer of the image carrier and the hard seal member, again resulting in damage to the outer layer of the image carrier.